Overview

N port virtualization (NPV) reduces the number of Fibre Channel domain IDs in SANs. Switches operating in the NPV mode do not join a fabric; they pass traffic between NPV core switch links and end devices, which eliminates the domain IDs for these edge switches.

Note:

NPV is available only for the following Cisco MDS 9000 switches: the Cisco MDS 9124 Multilayer Fabric Switch, the Cisco MDS 9134 Fabric Switch, the Cisco Fabric Switch for HP c-Class BladeSystem and the Cisco Fabric Switch for IBM BladeCenter.

With NPV a fabric or blade switch appears as a host to the core Fibre Channel switch, and appears as a Fibre Channel switch to the servers in the fabric switch or blade switch. NPV aggregates multiple locally connected N ports into one or more external NP links, which shares the domain ID of the NPV core switch among multiple NPV switches. NPV also allows multiple devices to attach to the same port on the NPV core switch.

NPV uses N port identifier virtualization (NPIV) to get multiple FCIDs allocated from the core switch on the NP port.

A switch is in NPV mode after a user has enabled NPV and the switch has successfully rebooted. NPV mode applies to an entire switch. All end devices connected to a switch that is in NPV mode must log in as an N port to use this feature (loop-attached devices are not supported). All links from the edge switches (in NPV mode) to the NPV core switches are established as NP ports. NPIV is used by the switches in NPV mode to log in to multiple end-devices that share a link to the NPV core switch.

For a complete description of NPV, refer to the Cisco MDS 9000 Family CLI Configuration Guide.

Initial Troubleshooting Checklist

Troubleshooting an NPV problem involves gathering information about the switch configuration and connectivity of individual devices and the entire SAN fabric. Begin your troubleshooting activity by using this checklist:

Checklist

Check off

Verify that the NPV core switch supports NPIV and that NPIV is enabled.

Verify that NPV is enabled on the NPV device.

Verify that the ports are properly connected.

For all NPV core switch links, ensure that the port mode on the NPV device is NP port, and ensure that the port mode on the NPV core switch is F port.

Ensure that the VSAN values configured on both sides of NPV core switch link are the same.

For all the device links, ensure that the port mode on the NPV device is F port.

Ensure that the VSAN value configured on the device links is correct.

Verify the status of servers and external interfaces, using the show npv status command.

Limitations and Restrictions

NPV core switches must support NPIV.

You cannot manually assign the server interfaces to a specific NPV core switch link. If an NPIV capable module is connected to the server interface, all of the logins from the NPIV-capable module will use the same NPIV core switch link.

Remote SPAN is not supported.

A maximum of 16 VSANs are supported on an NPV device.

Local switching is not supported; all traffic is switched via the NPV core switch.

Only F, NP, and SD ports are supported in NPV mode.

CFS and QoS are not supported.

IVR, SDV, and FICON are not supported.

If an NPV link failover occurs, servers that are booted over the SAN with NPV will temporarily lose access to their boot LUNs.

Common CLI Commands for NPV

Note:

Because the output is based on name server database information, the show fcns database npv commands can be run from any MDS switch running SAN-OS 3.2(1) or later. The switch does not need to be NPV enabled.

To display the status and VSAN membership of the different servers and external interfaces, and to verify that NPIV is enabled on the switch, enter the show npv status command.

Common Problems with NPV

This section includes common NPV issues.

Moving the Login of an End Device

If an uplink fails, all of the end devices that were logged in through the failed uplink are logged out. When the end devices log in again, the login requests are evenly distributed between all the operational uplink ports.

When a failed uplink comes back up, no existing logins are reassigned to that uplink. New logins are assigned to the operational uplink that has the least number of logins at the time; this is likely to be the previously failed uplink that has come back up.

You can move the login of an end device from its existing uplink to the one with least number of logins by performing the following tasks:

1. Enter the shutdown command on the server interface that needs to be migrated.

2. If the state is Failed with the reason "NPIV is not enabled in upstream switch," you must enable NPIV on the core NPV switch.

The NPV core switch is defined as an upstream switch on which NPIV is enabled. The NPV core switch receives traffic that is passed to it from a downstream switch that has NPV enabled on it. A switch that is in NPV mode does not switch traffic; instead, it passes traffic to the upstream NPV core switch on which NPIV is enabled.

After NPIV is enabled on the core NPV switch, the port should automatically come up (unless there are other issues).